And then add linear gradients of this color (color -> transparency) on each side. It is important to set the opacity to 100% and to start inside the boundaries of document.

Pick the #efefef color, which is pretty white-alike. Then add another guide in View > Add guide, but this time- horizontal on the distance of 20px. I also added some additional horizontal guides so later I will just move them using move tool. Don't care that our paper texture didn't covered the whole document. On top we will have a dark header that will cover the background, so as you can see it doesn't matter. Now choose the Rectangle tool and make a big shape from this corner:

To somewhere here on bottom so our whitey shape will be 960px wide:

To this moment we should end up with something like that below which is our base for later design:

Step 7 - header

We will start designing from single-blog-post page. So our header shouldn't be too large. I've putted my guide 340px horizontally from top- you can do the same as well. I've made a new group for layers and named it 'top'. With rectangle tool make a shape to the top from our guide. The color I used is #12101b. Then add some noise to it with Filter > Noise > Add noise, but really, just a bit. Make it uniform and don't go higher than 1%.

Colors on header and below are really differ, but for better contrast we can add 1px line below header shape. Pick Single Row Marquee Tool and select the line just below the shape. Then fill it with pure white color (Press SHIFT + F5 to open fill window).

Now all the layers will be in a clipping mask of header's shape layer. To do a clipping mask move the cursor between layers in layer's window. Hold alt, and when cursor will change, left-click. Here's a screen from my oldest tutorial. You will notice an arrow next to the thumbnail of layer so you will know it is clipped.

Now I will show you simple space trick that I developed some time ago by mistake, yet I like it pretty much. Oh, remember to create everything on new layers. I won't quote this every time we need a new layer so just have it in mind that more layers you have- the bigger flexibility you gain. So before we will go further just repeat few times in your head: "new layer, new layer...". Alright, CTRL+Click on the header shape's thumbnail in layer's window so you will get the selection (The reason to make it is just saving memory from unneeded data). Then press D so your colors will switch to black and white.